Since semiconductor devices including compounds such as GaN, AlGaN, and the like have many advantages such as wide and easily adjustable bandgap energy, the semiconductor devices are being variously used as light emitting devices, light receiving devices, and various diodes. Particularly, light emitting devices using the group III-V or II-VI compound semiconductor materials of semiconductors may be p-b junction diodes having characteristics in which electrical energy is converted into light energy and may be produced by using compound semiconductors such as the groups in the periodic table to realize various colors by adjusting a composition ratio of the compound semiconductors.
In such a light emitting device, when a forward voltage is applied, electrons in an n-layer and holes in a p-layer are coupled to each other to emit energy corresponding to an energy gap between a conduction band and a valance band. Here, the energy may be mainly emitted in the form of heat or light, and also, when the energy is emitted in the form of the light, it becomes a light emitting device.
The light emitting device may adjust a composition ratio of semiconductor compounds to realize various colors. For example, the light emitting device may be a blue light emitting device, a green light emitting device, an ultraviolet (UV) light emitting device, or a red light emitting device.
A general light emitting device includes a light emitting structure including an active layer and first and second conductive type semiconductor layers, which dopants different from each other, with the active layer therebetween. In addition, the light emitting device includes electrodes connected to the first and second conductive type semiconductor layers.
The general light emitting device increases in operation voltage and decreases in output voltage due to a current crowding phenomenon which occurs by concentrating current around the electrodes. Also, the electrodes may absorb or block the light to deteriorate light extraction efficiency.